This invention relates to improvements in ball valves and particularly to the movable spring-loaded seat utilized to seal the inlet port of the valve body from the exterior of the valve ball.
In conventional ball valves, considerable difficulty has been experienced in applications involving high pressures and higher temperatures, i.e., over 1,000.degree. F., particularly where the fluid stream contains appreciable quantities of solid particles. The solid particles tend to pack around the movable seat and the thermal cycling and high temperatures cause relatively large thermal distortions as the solid particles expanded with temperature. The packing of the solid particles around the movable seat limited its movement, and when coupled with the thermal distortion which caused relative motion of the seat toward the ball of over 0.01 inches, in some cases, caused a binding between the ball and movable seat. Such binding made operation of the ball valve difficult and contributed to increased wear between the valve ball and the seat.
Accordingly, one primary feature of the present invention is to provide an improved ball valve that may be operated at sustained temperatures above 1,000.degree. F.
Another feature of the present invention is to provide an improved seat spring in the form of a spring washer that can absorb greater flexing movement due to thermal distortion and maintain a satisfactory seating force without exceeding allowable stresses in the spring.
Yet another feature of the present invention is to provide a conical surface on the inlet throat of the valve facing the spring washer that provides a wedge-shaped void therebetween in order that any accumulation of solid particles will be moved and released by the flexing of the seat spring, eliminating the possibility of an accumulation of solid particles restricting the movement of the spring and seat to cause binding between the ball and seat.
Still another feature of the present invention is to provide an improved ball valve where the spring washer is sealed to the valve body and the movable seat is sealed to the valve ball on the inlet side of the ball, thereby developing additional seating force when the differential pressure across the ball is increased, such as when the ball valve is closed.